class Phone:
    __current_voltage = None

    def __init__(self, voltage):
        """
        核心CPU对应的电量
        :param voltage: 核心参数，不像让外部访问到这个函数
        """
        self.__current_voltage = voltage

    def __keep_single_core(self):
        """
        打印当前函数
        :param self:
        :return:
        """
        print("让CPU处于单核状态运行")

    def call_by_5g(self):
        if self.__current_voltage > 15:
            print("现在开始更新系统")
        else:
            print("当前电量过低，无法更新系统，请及时充电")
            self.__keep_single_core()

phone_15pro=Phone(12)
phone_15pro.call_by_5g()